CNC lathing

[bandsawgal]

Hi, I am new to the forum and was wondering if there are any CNC operators out there that have worked on the (Fanuc) CNC wood lathing machinery? The one in our shop is not holding down the plywood properly and I was wondering if the vacuum/pump was the reason or perhaps there is something else? I am told that we have a 9 hp on it now but the sales guy from the company says maybe it needs a 25 hp to make a better suction difference. The catch is that a 25 hp pump is costly and I felt the sales company should have provided it since they were told in advance what our company would be using it for. ANyhow.. I don't know much about the machine yet as I am training on it starting next week. I just thought I might get an opinion or two so I could help my boss out before he makes any costly adjustments. Also, if anyone has any used instruction videos, on this machines functions and maintenence, I would love to hear from you since here in Quebec there doesn't seem to be anywhere to go to train for operations (in English) that I can find.

[handi]

Bandsawgal,

I sell 3 axis CNC's and have been programming and operating them for over 5 years.

Whether or not the pump is adequate depends on many factors. How large an area are you trying to hold down? (Vacuum holding is a function of square inches)Are you using a fixture board or a bleed board. (I'm guessing fixture) What is the CFM rating for the pump, and how many inches of murcury does it draw at the inlet?

Please feel free to e-mail me with more specifics and I'll be happy to try and help you figure out how you might resolve this.

Ralph

[bandsawgal]

Hi! The board area is approx. 5ft (sq) Since I am new to this, could you explain the difference between fixture and bleed board? My boss is using a lower grade plywood on it. He tried also using LDF which I suppose is like MDF? I don't want to seem dumb but it is all new to me (I usually work on the bandsaw and radial saws and routers) and I have not yet been trained on the specifics of this machinery.
I will ask about the CFM rating (?) and the inches of mercury that it draws and get back to you. Thanks for answering my message that was nice of you.

[handi]

Bandsawgal,

A bleed board is a flat piece of porous material that the vacuum "bleeds" through to hold the part. A fixture board is non-porous and has a gasket that traps the vacuum under the part, thus holding it in place.

The bleed board by nature leaks a great deal of vacuum. It is a good solution for fairly large parts. Because it leaks, you need a lot of CFM but not so much draw. (inches of mercury)The bleed board also works on any part large enough for the vacuum to hold. In other words, it is not specific to the part.LDF is the right material to use for a bleed board

A fixture board is designed to hold specific parts. The gasketed vacuum area is shaped to each part. It is designed NOT to leak, so CFM is not the priority, but draw is. You can hold much smaller parts with a fixture board, but again need boards for each part or group of parts.

Not to be insulting, but are we really talking about a lathe here? I really cannot picture how a spinning part can be held by vacuum. I used to sell CNC lathes, and every one of them used a pnuematic center to hold the part by it's ends.

If, in fact, we are talking about a CNC router, I can help you out a great deal with proper fixturing and vacuum hold down technique. I've been doing this for over 5 years now.

Hope this helps,

Ralph

[bandsawgal]

Hi! Wow you know a lot! Yes its a CNC Router . The machine says Fanuc (ANDI). I'm sorry if I used the word "lathe" inappropriately. But in all honesty, I'm working in a mill with people who only speak French and I don't speak it well yet,so much gets lost in the translation. Asking questions about the machine is difficult. I was supposed to be trained on it this week but ......(long story)
I really want to learn to operate this machine (for myself) so I'm continuing to research and investigate it further on my lunch hours. There are no courses here for some ungodly reason. That is why I initially asked if anyone had any used video tapes or books on the subject that they could share. Anyhow, you have been very nice to help me and explain things. Sorry about the confusion. My boss has so far made a grid with smaller holes to hold down the wood better than the suction holes on the table but they are still having problems with it and the plywood tends to move slightly off. I'd love to solve the problem but I really don't know how without understanding the machine better.

[handi]

Bandsawgal,

Please do not feel stupid. The vacuum hold down system can be tricky and a great many people do not understand how it works at first.

First of all, for a 5 foot square bleed board, you should be ok with a 9hp pump, as long as it is drawing 70 CFM or more. Here are a few things to try:

1) Flatten the bleed board. Get a fly cutter and mill the top of the board flat. Try to run your programs so that the bit cuts only a few thousandths into the bleed board. When the board gets chewed up a bit, resurface. A flat surface will give you the best holding.

2) Be sure that the bleedboard is totally clean before you put your part down. Even a little dust will act like bearings. Vacuum it off, then blow it off with air.

3) What types of bits are you using, and at what speeds? The board is moving because of the side pressure of the cutting. Sprial bits create far less side pressure that straight bits, allowing for higher feed rates. A good starting point to work from is 18,000 rpm and 200 inches per minute feed. If that works, lower the RPM and increase the feed until either the board moves or the cut quality falls off.

4) any vacuum area that is not covered by the board you are milling should be covered by something. I recommend laminate or that corregated plastic stuff that looks like cardboard. Just lay a few pieces on to cover as much area as you can. That will increase the holding power.

5) check your plywood for bowing. If at all possible, the board should crown up in the center rather than the edges. You have maximum holding in the center.

6) Check the vacuum lines from the table to the pump and make sure that you have no leaks.

7) If you can, seal the edges of the bleed board. That will reduce leakage.

8) Here is a silly question, but needs to be asked. Have you checked the gasket under the bleed board? You should have a foam rubber gasket all the way around the edge of the bleed board to seal the phenolic table and bleed board. Also, if the bleed board does not cover the entire table, be sure that any exposed vacuum holes in the phenolic table are sealed.

Check into these items and if none of that solves the problem, there is a way to do what you want that I can tell you about, but it's a last resort.

Hope this helps,

Ralph

[bandsawgal]

Hi Ralph, Thanx so much for your help. I'm going in to work tomorrow armed with all the info. Today they ran it and used some laminate to cover up the exposed vacuum holes. Its running at 18,000 rpms as far as I know. We have all different bits so I am not sure what they have been using. So far they have broken two bits (training the guy who got the job)..I'm pretty sure they haven't checked the gasket under the bleed board so that is somthing to look at. Then I'll tell them to check the vacuum lines from the table to the pump as you suggested. Gee you are smart. How did you ever get into all this anyway? And when you say "back to the shop", does this mean you run a mill of your own? In the mill today, I cut pieces out faster on my bandsaw than the guy who was operating the CNC. My boss and I laughed over that one since we've both seen professionals operate the CNCs at the woodworking shows.I suppose the CNC router will eventually replace my job of cutting patterns altogether one day. But thats progress eh...
Thanx again Ralph and have a good day in the shop.

[handi]

Bandsawgal,

LOL, I was working in a shop doing plastics for them. They bought a CNC and I told them flat out that I wanted to learn it. Next thing I know I'm programming two machines, doing setups and fixtures. It is a wonderful and valuable skill to have.

As far as my signature line, I don't yet have a fully professional shop. I am rebuilding a 170 year old barn that will become my shop hopefully this summer. In the meantime, I design and build projects that I have been selling as freelance articles to Woodworker's Journal magazine. My first jig appears in the September/October issue next month.

Let me know how things progress at work.

Ralph

[bandsawgal]

Hi Ralph, Wow, you sound pretty busy with all your projects.
Guess what? I started training on the CNC today for the first time! I was really excited but there were lots of glitches in the programming that have to be ironed out. I'm not sure that my boss understands some of the procedures. For example, when I cut out the templates with the program in the machine, the wood began to shift (the edge areas of the board exterior to the cuts)This is still due to suction but its much better now that they covered and checked all other areas as you mentioned.
My boss shut the spindle down and manually raised the Z then he flicked the program into reset. I'm not sure it should be done like that but he says thats what works. Then the next time that I was instructed to do that when the plywood shifted, I noticed the spindle kept running?? Its small things like that which confuse me. I was looking through the operations manual but my boss needs it and I can't bring it home to study it.
The other guy on the machine said that the spindle dropped out of the machine when he was doing the setup.. lol...This guy plays with the buttons all the time..(I had to tell him today what a cursor was...(see what I'm up against) hehe... (oh that wasn't nice.. LOL
Could that be something to do with a program error or heres a good question...is there a button on the control panel or a command that might automatically release the spindle? I went over all the buttons on the panel and actually have one that I have no clue what it does! Its not in the manual but it seems to be related to the Z axis as the symbol on it looks like that with an arrow. Do you know this button and its function..
Anyway, I want to learn it well and know the machine inside out. Programming seems interesting too and I've been looking at the codes to understand how it all works. How did you ever figure out the programming part? Did you have to take a course?
Well I'd better let you get back to all your fun woodworking and the shop as i think I've already written you a book here lol...sorry about that...I'm just hopelessly enthusiastic over such things.. So enjoy and have a nice weekend.
Bandsawgal

[handi]

Bandsawgal,

I do have to admit that I'm not as familiar with the Fanuc controller as I'd like, but if you can send me a good picture of the controller face plate it might be easier to "see" which buttons you are refering to when you ask questions.

When you say the "spindle drops out" what exactly do you mean? Technically, the spindle is the entire router motor. I suspect that you are refering to the tool holder?

Two more ideas for improving hold down:

1) After placing your work piece on the table,use plywood pieces to cover the unused table as you are doing now, but butt them up firmly against the edges of the workpiece. This will help hold the workpiece from sliding around.

2) The ultimate solution is "onion skinning". See, each cut you make through the workpiece lessens the vacuum seal and weakens the hold. Write your programs with two passes. The first pass will cut all but .020" through the material, the second pass finishes the cut. You loose no vacuum pressure during the heavy cut of the first pass, and the side pressure of the second pass is virtually nothing since you are only cutting .020" of material. If the parts are really small, leave the onion skin, and use a laminate trimmer to remove the skin off the machine. This way you can be doing this while the next set of parts is milling.

As far as knowing the G-Code, I had to learn it when I got started programming. It is not terribly difficult to learn, but the newer software pretty much eliminates the need to know it.

By the way, where is your shop located? It might be worthwhile for you folks to get a day or two of training from either Anderson, or an independant trainer. Depending on where you are located, I can recommend some folks.

Have fun and stay in touch,

Ralph